Veteran BBC journalist John Humphrys is appalled by the quality of many television programmes today.
Delivering the McTaggart Lecture at the Edinburgh Television Festival, he was particularly scathing about "reality TV".
This is an edited version of his speech:

I was not making any great protest by abandoning television five years ago. I moved house, my old telly wouldn't work and I put off getting a new one until the builders had moved out. That took three months and I realised that I hadn't missed it, so I just never got around to buying another one.

That gives me a unique perspective. I have watched a lot of television in the past few months - and it has changed a lot in five years.

First, let me dispel a myth that pops up as regularly as the weather forecast: there's nothing worth watching these days. It's rubbish. The quality of the best television is not just as good as it ever was. It is even better.

But ... there's the rest of it. A vast amount is simply mediocre. One of the most senior executives in the business described it to me as carbohydrate television. You watch it ("consume" might be better) because it's there. After an hour or two you feel as if you've wasted your time, but what the hell. It probably hasn't done you much harm and if it leaves you feeling a bit bloated ... well, you can search out a bit of quality stuff - a bit of protein to go with the carbohydrate.

We all know why there is so much of it. Michael Grade has talked about the "market-driven drift towards programme-making as a commodity". This wouldn't matter if all this stuff were cheap, but it costs money, and that's money that can't be spent on decent programmes. The fashionable defence of it is to say that it is "no-brow" television: not high-brow, not low-brow - just no-brow. It is no-brow because it is no content, no nourishment, no good.

There is, of course, another defence against this kind of television. It's the Blue Planet defence: "Yes there's some lousy television around, but what about The Blue Planet? What about Walking With Dinosaurs...?" Well, you might - just - get away with that. But it is not a defence against bad television.

The first principle of the Hippocratic oath, which doctors have been swearing for 2,500 years, is "Do no harm". It's not a bad principle for broadcasters. The good television of today is better than the best television of the old days. The bad television is worse. It is not only bad, it is damaging. Meretricious. Seedy. Cynical.

Good television does not balance the bad. Not if it coarsens and brutalises and turns us into voyeurs. The good cannot pay the dues of the bad when the bad is indefensible. And some of our worst television is indefensible. It does harm.

I was shocked by some of what I saw when I came out of my Rip Van Winkle state. So much of it seemed not just vulgar and obsessed with sex, but altogether more confrontational than I'd remembered. The violence of the language surprised me. It seemed almost impossible to switch on without encountering some sort of aggression, even in the soaps.

So that's one big change, but it's been an incremental one. There has been another, seminal, change that made this Rip Van Winkle wonder if he had woken from his long sleep not just in another time, but in another place. It is, of course, so-called reality television.

Reality implies authenticity and honesty. And whatever some of this stuff may be, it is not authentic and it is not honest. This is not just bad television in the sense that it's mediocre, pointless, puerile even. It's bad because it is damaging. Remember: first, do no harm.

The influence of reality programmes has been out of all proportion to their number. They have infected the mainstream of the medium. History is one small example - now it has to be "living" history. Commissioning editors have less of the schedule to play with; they become risk-averse. Originality suffers.

Then there is the cult of celebrity, which fosters values that are utterly shallow and kill real ambition. We tell kids what matters is being a celebrity and we wonder why some behave the way they do. And what about the "lucky" ones, the ones who make it into the house, on to the screen? Most survive unscathed - so far as we know. But then, we would not know if they were damaged, would we, because we lose interest once they are no longer "famous". BB5, we were told, would "get evil". The house would be made more claustrophobic to "prompt the explosion of any tensions". And when the explosions duly happened, what are we told? "The welfare of the housemates is always our overriding concern". Note the "always". Do I need to join the dots?

In society as a whole, reality television erodes the distinction between the public and the private, which is a profoundly important aspect of our culture. Much more worrying is its coarsening effect. It turns human beings into freaks for us to gawp at. And don't tell me it's just entertainment. You can't use people with real lives and real problems and real children as "just entertainment". Well, you can, but it's corrupting. The first time I watched Big Brother live there were two men lying on beds and talking about women. Or rather "crappity smacking women". And talking about their responses to them. Or, rather, "my crappity smacking stiffy". My, how we've pushed back the boundaries of television. How proud we should be.

Let me give you a quote: "To apply broadcasting to the dissemination of the shoddy, the vulgar and the sensational would be a blasphemy against human nature." That was Lord Reith. But what did he know? Patronising old toff.

You may ask why I'm attacking reality TV when it's in its death throes. Well, because it's not. What happened when Big Brother ratings were down last year? The ratchet effect took over. We had to be shocked that bit more. That's what always happens when ratings are the only measure. And ratchets work only one way. Even when this genre exhausts itself, it will leave behind an audience that has been desensitised. The ratchet has been at work.

There has always been a clash between freedom, especially freedom of expression, and the conservative wish to preserve values. In the 60s, Mary Whitehouse was taken apart by the liberal elite, who defended Lady Chatterley and the Oz publishers, arguing - in my view rightly - that it was not just censorious but stupid to pretend that sex happened only in the marital bed. This was a genuine debate between different views of what was good for society.

What's happening now is different. This is a battle between people who are concerned about society and those whose interest is simply to make programmes that make money. Those who fought for the word crappity smack in Lady Chatterley didn't do it to make money. Now the cash registers go ker-ching every time there's a fumble beneath the bed sheets.

In the bad old days we had paternalists trying to capture the masses for what they believed in their patrician way to be good. Now we have businessmen calculating how much they can get away with to titillate or to outrage the masses and deliver the profits. Which is worse?

Some of the people who bring us junk TV admit there may be something in what I'm saying. They have a defence: the free market. "Sorry," they say, "it's out of our hands." This brings us to the heart of it. What can people who are worried do about a television market that is increasingly open and free from regulation?

If we tried to limit the harm, it would not amount to censorship. People who want the stuff that I find offensive can always get it if they're prepared to pay. Let them. The question for us is: do we want to keep part of the television world within the boundaries of regulation?

Ofcom is examining its regulatory role in relation to public service broadcasting. It will soon be coming out with the second stage of its conclusions. It is interested in what it calls the "citizen rationale" for regulation: that is "to secure wider social benefits".

Economists talk about "merit goods" - a useful concept to apply to television. Public service broadcasters must provide goods that individuals and advertisers are not prepared to pay for. I'd like to suggest to Ofcom that there is an obverse of merit goods: debit goods. Just as it intervenes to make sure that merit goods are provided on terrestrial channels, it should intervene to prevent the supply of debit goods. It may, indeed, be moving in that direction. It's planning to remove prescriptions on taste and decency and replace them with guidelines on harm and offence. Much better.

Some say Ofcom may not have the power to muck about with its regulatory framework. Well, parliament should give it that power. It's also for parliament to decide if terrestrial commercial channels need special protection in return for a more committed public-service approach that avoids harm.

The BBC's responsibilities in this brave new world are greater than ever. It has recently rediscovered the value of genuine public service broadcasting, or so we are told. Some cynical souls make a connection between that and charter renewal.If that's true, so what? That's what the charter process is for, isn't it?

The BBC has avoided the excesses of reality television. But what of that other vital aspect of public service broadcasting: news - the most important thing we do. By a mile. If we get it wrong, we forfeit the right to exist.

We are living in what everyone seems to call the post-Hutton era. If this means we should make ever greater efforts to get things right, that's fine - but we've always tried to do that. But it seems to imply that our political journalism needs somehow to be different. This is the bit that worries me.

It's usually linked to the idea that people have lost interest in politics and that's somehow our fault. Certainly fewer people bother to vote, but we've had 12 years of economic growth. In a culture where getting and spending is the big preoccupation, it's hardly surprising they're a bit apathetic. But if we do have some responsibility for apathy, what might it be?

It was Greg Dyke's view that we hadn't faced up to the fact that politics is boring and it's our job to make it less boring. If that's true, how come so many people were voting when Brian Walden was supposedly boring the pants off us on Weekend World, and there were other political programmes that were just as analytical, just as (in the Dyke view) boring.

Even if it were true, it's not our job to make it fun. It's a serious business and it's our job to report it seriously. We shouldn't be trying to lure people into politics by pretending that it's just another game show. Greg got it wrong.

But there's a more serious charge: that our own cynical approach has turned people off politics. This is the thesis of John Lloyd's book, What the Media Are Doing to Our Politics. He says that the Gilligan affair must be seen in the context of a wider media narrative that assumes the government lies about everything. This is a serious charge.

The question is not whether there is cynicism about politics, but whether journalism is the cause. If you believe that, then, yes, we need a post-Hutton era in which we purge this virus. But I don't believe it. For one thing, don't politicians have some responsibility for it? What about the so-called Tory sleaze and the way Labour made capital from it? Or the war many believe (rightly or wrongly) they were misled into supporting?

Lloyd argues that the threat posed to democratic institutions is at its greatest "when the media is at its most fearless". What a remarkable thing for a journalist to say. We threaten democratic institutions when we are fearless.

Well, we should be fearful of many things: getting it right, abiding by the law, genuine impartiality. We should not be fearful of standing up to those in power. That is our job: to be fearless in the face of power. In any era.

I have not personally been leaned on by the bosses to go easy in the wake of Hutton. But it's not that simple. I've read about the "knives being out". Well, I can't remember when they weren't. What matters is something more subtle. The Lloyd thesis is not his alone. He has some powerful supporters.

It's easy, in the shockwaves created by the Hutton report and all that preceded it, for confidence to be replaced by uncertainty, particularly when the phrase "post-Hutton BBC" is used to suggest that we have been cowed. It's easy for producers and editors to ask not only "Is this right?" (as they must) but "Who might we be upsetting?". Let me steal a phrase from Lord Hutton himself. It is possible to be "subconsciously influenced" into thinking this is what your masters might want.

We need more, not less, in-depth interviewing of politicians. The idea that tough questions prevent politicians from giving answers, and gentle chats seduce them into candour is, frankly, risible. We need more, not less, investigative journalism. We need much more straightforward political analysis. Public service broadcasting can and must make an important contribution to the democratic process. It can do so only if not cowed by those in power.

Halfway through my period of abstinence, I began to think television didn't matter much. I didn't miss it as entertainment; I have no great interest in sport, and I get all the news I need from newspapers, magazines and Radio 4. But you can't escape from it, its influence is everywhere. And I don't want to.

I watched Life of Mammals with my four-year-old son on my lap. He was wide-eyed with wonder. It's not cutting edge. It's not shocking. It's old hat. But, like the very best of television, it really opens new windows on to the world.

It may seem odd to end on this slightly soppy note. But I've been reminded after my long absence that television can enrich lives. It can lift our spirits. It can give us a deeper understanding of the human condition. It can help maintain the momentum that takes us from barbarity to civilisation. There is good stuff out there. Don't allow it be dragged down. First, do no harm.